Seal with backup seal

ABSTRACT

A sealing arrangement has a turbine static structure with contact surfaces, a bearing compartment with contact surfaces, and a cavity between the turbine static structure and the bearing compartment. There are also two seals, wherein each seal is configured to contact the turbine static structure and the bearing compartment.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Reference is made to U.S. Pat. App. Ser. No. ______ entitled “BEARINGCOMPARTMENT SEAL” and U.S. Pat. App. Ser. No. ______ entitled “FLANGETRAPPED SEAL CONFIGURATION”, which are filed on even date by the sameapplicant and are assigned to the same assignee as this application.

BACKGROUND

The present invention relates generally to gas turbine engines, and moreparticularly to a seal arrangement of a gas turbine engine.

A gas turbine engine typically includes a high pressure spool, acombustion system and a low pressure spool disposed within an enginecase to form a generally axial, serial flow path about the enginecenterline. The high pressure spool includes a high pressure turbine, ahigh pressure shaft extending axially forward from the high pressureturbine, and a high pressure compressor connected to a forward end ofthe high pressure shaft. The low pressure spool includes a low pressureturbine, which is disposed downstream of the high pressure turbine, alow pressure shaft, which typically extends coaxially through the highpressure shaft, and a low pressure compressor connected to a forward endof the low pressure shaft, forward of the high pressure compressor. Thecombustion system is disposed between the high pressure compressor andthe high pressure turbine and receives compressed air from thecompressors and fuel provided by a fuel injection system. A combustionprocess is carried out within the combustion system to produce highenergy gases to produce thrust and turn the high and low pressureturbines, which drive the compressors to sustain the combustion process.

Both the high and low pressure spools include alternating cascades ofstators and rotors in order to work on the primary fluid in the flowpath. Because the stators are stationary but the rotors rotate, bearingsare necessary to permit the relative motion. Bearings can be situated inbearing compartments that provide oil to the moving parts forlubrication.

The combustion system heats the primary fluid in the flow path to veryhigh temperatures, so both the high and low pressure turbines utilizecooling air from the high and/or low pressure compressors. This coolingair can be fed into a bearing compartment in order to cool and purge thebearing compartment of any stray oil that has leaked out. Because theboundaries of the bearing compartment can be formed by severalcomponents, seal arrangements are utilized between the components tocontrol fluid flow.

SUMMARY

According to one embodiment of the present invention, a sealingarrangement has a turbine static structure with contact surfaces, abearing compartment with contact surfaces, and a cavity between theturbine static structure and the bearing compartment. There are also twoseals, wherein each seal is configured to contact the turbine staticstructure and the bearing compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side cross-section view of a gas turbine engine.

FIG. 2 is a cross-sectional view of a mid-turbine frame and a bearingcompartment at the top of the gas turbine engine.

FIG. 3 is a cross-sectional view of a sealing arrangement.

FIG. 4 is a cross-sectional view of an alternate embodiment sealingarrangement.

FIG. 5 is a cross-sectional view of an incorrectly assembled sealingarrangement.

FIG. 6 is a cross-sectional view of a sealing arrangement with drainpathways at the bottom of the gas turbine engine.

FIG. 7 is a cross-sectional view of an alternate embodiment sealingarrangement.

DETAILED DESCRIPTION

In FIG. 1, a cross section of gas turbine engine 10 is shown. AlthoughFIG. 1 depicts a gas turbine engine typically used for aircraftpropulsion, the invention is readily applicable to gas turbinegenerators and other similar systems incorporating rotor-supported,shaft-driven turbines. Shown in FIG. 1 are gas turbine engine 10, fan12, low pressure compressor (LPC) 14, high pressure compressor (HPC) 16,combustor section 18, high pressure turbine (HPT) 20, low pressureturbine (LPT) 22, fan case 24, LPC case 26, HPC case 28, HPT case 30,LPT case 32, low pressure shaft 34, high pressure shaft 36, exit guidevanes 38, injectors 40, HPT blades 41, LPT blades 42, support rotor 44,vane airfoil sections 46, case section 48, supply line 50, rod 52,mid-turbine frame 54, bearing compartment 56, inlet air A, primary airA_(P), secondary air A_(S) (also known as bypass air), and longitudinalengine centerline axis C_(L).

In the illustrated embodiment, gas turbine engine 10 comprises adual-spool turbofan engine in which the advantages of the presentinvention are particularly well illustrated. Gas turbine engine 10, ofwhich the operational principles are well known in the art, comprisesfan 12, low pressure compressor (LPC) 14, high pressure compressor (HPC)16, combustor section 18, high pressure turbine (HPT) 20, and lowpressure turbine (LPT) 22, which are each concentrically disposed aroundlongitudinal engine centerline axis C_(L). Fan 12 is enclosed at itsouter diameter within fan case 24. Likewise, the other engine componentsare correspondingly enclosed at their outer diameters within variousengine casings, including LPC case 26, HPC case 28, HPT case 30 and LPTcase 32. Fan 12 and LPC 14 are connected to LPT 22 through low pressureshaft 34, and together with fan 12, LPC 14, LPT 22, and low pressureshaft 34 comprise the low pressure spool. HPC 16 is connected to HPT 20through high pressure shaft 36, and together HPC 16, HPT 20, and highpressure shaft 36 comprise the high pressure spool.

During normal operation, inlet air A enters engine 10 where it isdivided into streams of primary air A_(P) and secondary air A_(S) afterpassing through fan 12. Fan 12 is rotated by low pressure turbine 22through low pressure shaft 34 (either directly as shown or through agearbox, not shown) to accelerate secondary air A_(S) (also known asbypass air) through exit guide vanes 38, thereby producing a majorportion of the thrust output of engine 10. Primary air A_(P) (also knownas gas path air) is directed first into low pressure compressor 14 andthen into high pressure compressor 16. LPC 14 and HPC 16 work togetherto incrementally step up the pressure of primary air A_(P). HPC 16 isrotated by HPT 20 through low pressure shaft 34 to provide compressedair to combustor section 18. The compressed air is delivered tocombustors 18A-18B, along with fuel through injectors 40, such that acombustion process can be carried out to produce the high energy gasesnecessary to turn high pressure turbine 20 and low pressure turbine 22.Primary air A_(P) continues through gas turbine engine 10 whereby it istypically passed through an exhaust nozzle to further produce thrust.

After being compressed in LPC 14 and HPC 16 and participating in acombustion process in combustors 18A-18B (FIG. 1) to increase pressureand energy, primary air A_(P) flows through HPT 20 and LPT 22 such thatblades 32 and blades 42 extract energy from the flow of primary airA_(P). Primary air A_(P) impinges on HPT blades 41 to cause rotation ofhigh pressure shaft 36, which turns HPC 16. Primary air A_(P) alsoimpinges on LPT blades 42 to cause rotation of support rotor 44 and lowpressure shaft 34, which turns fan 12 and LPC 14.

In addition, a portion of primary air A_(P) can be bled off from atleast one of LPC 14, HPC 16, and in between LPC 14 and HPC 16 throughsupply line 50. This air is used for cooling components of HPT 20 andLPT 22, so the air travels through supply line 50 into rod 52. Rod 52 ishollow and is a component within mid-turbine frame 54. Mid-turbine frame54 is a turbine static structure that extends across the flow path ofprimary air A_(P). The cooling air is directed through rod 52 to LPT 22and towards bearing compartment 56. In the illustrated embodiment,bearing compartment 56 contains the number four bearing (i.e. the fourthbearing in from the front of gas turbine engine 10). Therefore, bearingcompartment 56 is positioned in between HPT 20 and LPT 22 alonglongitudinal engine centerline axis C_(L) such that bearing compartment56 is proximate HPT 20 and LPT 22.

The components and configuration of gas turbine engine 10 as shown inFIG. 1 allow for a portion of primary air A_(P) upstream of combustorsection 18 to be transported downstream of combustor section 18. Becausethis air is relatively cool (having not gone through combustor section18), the air can be used to cool components such as bearing compartment56. This is advantageous because the temperatures in HPT 20 and LPT 22would rise to excessively high levels if left unchecked. In addition,this air purges stray oil that has leaked within bearing compartment 56.

Depicted in FIG. 1 is one embodiment of the present invention, to whichthere are alternative embodiments. For example, engine 10 can be a threespool engine. In such an embodiment, engine 10 has an intermediatecompressor between LPC 14 and HPC 16 and an intermediate turbine betweenHPT 20 and LPT 22, wherein the intermediate compressor is connected tothe intermediate turbine with an additional shaft.

In FIG. 2 a cross-sectional view of mid-turbine frame 54 and bearingcompartment 56 is shown at the top of gas turbine engine 10. Mid-turbineframe 54 includes rod 52, fairing 58, inner case 60, and seal ring 62.Bearing compartment 56 includes bearing case 64, seal support 66, heatshield 68, and bearing 70. Also shown in FIG. 2 is sealing arrangement72 with piston seal 74.

In the illustrated embodiment, fairing 58 is adjacent to inner case 60,and inner case 60 is connected to rod 52 and seal ring 62. Inner case 60is also connected to bearing compartment 56, specifically to bearingcase 64, and cavity 65 exists between inner case 60 and bearing case 64.Bearing case 64 is connected to seal support 66, heat shield 68, andbearing 70. Between heat shield 68 and seal ring 62 is sealingarrangement 72. Sealing arrangement 72 includes piston seal 74 which ispositioned between seal ring 62 of mid-turbine frame 54 and heat shield68 of bearing compartment 56.

During operation of gas turbine engine 10 (shown in FIG. 1), pressurizedcooling air comes into rod 52 from supply line 50 (shown in FIG. 1).Most of the cooling air runs through rod 52 and is directed to LPT 22(shown in FIG. 1). Some of the cooling air is diverted into cavity 65for cooling of bearing case 64. In addition, this air purges cavity 65of oil that has accumulated in cavity 65, especially toward the bottomhalf of gas turbine engine 10 (shown in another embodiment in FIG. 6).The cooling air and oil escapes from cavity 65 past sealing arrangement72. Sealing arrangement 72 inhibits flow of fluid between mid-turbineframe 54 and cavity 65 by having piston seal 74 configured to contactseal ring 62 and heat shield 68. The amount of sealing provided bysealing arrangement 72 allows for enough flow to properly cool and purgecavity 65, but prevents an undesirably large amount of flow.

In FIG. 3, a cross-sectional view of sealing arrangement 72 is shown.Shown in FIG. 3 are mid-turbine frame 54 with inner case 60 and sealring 62; and bearing compartment 56 with bearing case 64, seal support66, and heat shield 68. Also shown in FIG. 3 are sealing arrangement 72with piston seal 74, frame fastener 76, and compartment fastener 78.

The region being depicted in FIG. 3 is adjacent HPT 20 (shown in FIG.1). Therefore, the space bordering mid-turbine frame 54 and bearingcompartment 56 on this side is rotor region 80. As shown in FIG. 2,mid-turbine frame 54 is rigidly connected to bearing compartment 56adjacent LPT 22 (shown in FIG. 1). But mid-turbine frame 54 is notrigidly connected to bearing compartment 56 adjacent rotor region 80.Sealing arrangement 72 is shown in more detail in FIG. 3 and is presentbetween mid-turbine frame 54 and bearing compartment 56. Sealingarrangement 72 inhibits flow of fluid from cavity 65 into rotor region80. In addition, sealing arrangement 72 inhibits reverse flow of fluidfrom rotor region 80 into cavity 65.

In the embodiment of FIG. 3, piston ring 74 subtends substantially acomplete circle and has a substantially rectangular cross-section withsides configured to contact mid-turbine frame 54 and bearing compartment56 for sealing. Piston ring 74 is made of a high-temperature alloy suchas a nickel or cobalt alloy (ex. Inconel® X-750 from the Special MetalsCorporation of New Hartford, N.Y.). Piston ring 74 is not a continuousring, so there is a joint in piston ring 74. While the joint in pistonring 74 could be a simple butt joint, instead a portion of piston ring74 is plug 74A that fits into channel 74B. This configuration onlyexists over a relatively small arc length of piston ring 74, with themajority of piston ring 74 being a solid cylinder. The joint in pistonring 74 allows for adjustability in the diametrical size of piston ring74, which aids in installation (as discussed later) and allows pistonring 74 to exert diametral tension on heat shield 68.

In the illustrated embodiment, inner case 60 is fastened to seal ring 62using frame fastener 76. Frame fastener 76 extends axially through innercase 60 and seal ring 62. Seal ring 62 is also connected to inner case60 by snap rim 82. Snap rim 82 overlaps and snaps onto snap portion 84of inner case 60. In addition, seal ring 62 includes groove 86 thatsubstantially surrounds the three radially outer sides of piston seal74. The lateral, opposing sides of groove 86 constrain piston seal 74axially and the radially outer side of groove 86 restrains piston seal74 radially. The lateral sides of groove 86 are annular contact surfacesfor piston seal 74. To inhibit flow from cavity 65, piston seal 74contacts the side of groove 86 that is closer to rotor region 80 (asdepicted in FIG. 3). To inhibit reverse flow from rotor region 80,piston seal 74 slides laterally over axial portion 90 due to thepressure differential across sealing arrangement 72. The result is thatpiston seal 74 contacts the opposite side of groove 86, which is theside that is closer to cavity 65 (this configuration is not depicted inFIG. 3).

In the illustrated embodiment, seal support 66 and heat shield 68 arefastened to bearing case 64 using compartment fastener 78. Compartmentfastener 78 extends axially through bearing case 64, seal support 66,and heat shield 68. Heat shield 68 includes radial portion 88 and axialportion 90. Compartment fastener 78 extends through radial portion 88,and axial portion 90 is a rim that attached at the radially outer sideof radial portion 88. Axial portion 90 extends beyond both sides ofradial portion 88 such that one side is positioned over seal support 66.The radial outer side of axial portion 90 is a cylindrical surface thatpiston seal 74 is configured to contact and restrains piston seal 74radially. Due to the configuration of piston ring 74, the contactsurface of axial portion 90 is substantially perpendicular to thecontact surfaces of groove 86.

In order to assemble sealing arrangement 72, bearing compartment 56 isassembled by fastening bearing case 64, seal support 66, and heat shield68 together. In addition, most of mid-turbine frame 54 is assembled,such as rod 52 (shown in FIG. 2) and inner case 60, without seal ring62. Then bearing compartment 56 and the partial mid-turbine frame 54 areconnected. Meanwhile, piston seal 74 is positioned in groove 86. Theuninstalled configuration of piston seal 74 has an inner diameter thatis smaller than the outer diameter of axial portion 90. Piston seal 74is then expanded to an expanded configuration having an inner diameterthat is larger than the outer diameter of axial portion 90. Piston seal74 is fixed in this expanded configuration using, for example, adhesivein the joint of piston seal 74, adjacent plug 74A and channel 74B. Sealring 62 is then snapped onto and fastened to inner case 60 such thatpiston seal 74 surrounds heat shield 68. Piston seal 74 is then unfixedfrom the expanded configuration, allowing piston seal 74 to contactaxial portion 90. Piston seal 74 grips on to axial portion 90 due todiametic tension, although piston seal 74 is slidably movable alongaxial portion 90. This unfixing includes the removal of the adhesive inthe joint, for example, using chemicals and/or heat (including heatapplied by operating gas turbine engine 10, shown in FIG. 1).

The components and configuration of sealing arrangement 72 as shown inFIG. 3 allow for piston seal 74 to be positioned between mid-turbineframe 54 and bearing compartment 56. Using piston seal 74 isadvantageous because piston seals have significantly more mass than someother types of seals, for example, w-seals. Therefore piston sealsprovide thermal resistance and protection to components that areadjacent rotor region 80. In addition, piston seal 74 allows for somecooling air to transport stray oil out of cavity 65.

Depicted in FIG. 3 is one embodiment of the present invention, to whichthere are alternative embodiments. For example, piston seal 74 can beadapted to allow virtually no flow through sealing arrangement 72. Insuch an embodiment, purging of bearing compartment 56 would beminimized.

In FIG. 4, a cross-sectional view of an alternate embodiment sealingarrangement 172 is shown. Sealing arrangement 172 shares some of thecomponents with sealing arrangement 72, such as bearing compartment 56and piston seal 74, but has other components that are different, such asmid-turbine frame 154. In general, piston seal 74 is positioned betweenand is configured to contact sealing ring 162, inner case 160, and heatshield 68.

In the illustrated embodiment, mid-turbine frame 154 includes inner case160 and seal ring 162. Inner case 160 includes flange 192 that extendsradially inward from snap portion 84. While flange 192 could have aplain cylindrical shape, flange 192 has a scalloped radially inner endcomprised of a plurality of fingers 194. Flange 192 axially constrainspiston seal 74 and is the lateral annular contact surface that pistonseal 74 is configured to contact in order to inhibit reverse flow (thisconfiguration is not depicted in FIG. 4). Seal ring 162 includes rabbet186 which axially and radially constrains piston seal 74. Rabbet 186also serves as the lateral annular contact surface that piston seal 74is configured to contact in order to inhibit normal flow (as depicted inFIG. 4) out of cavity 56. Due to the configuration of piston ring 74,the lateral contact surfaces of flange 192 and rabbet 186 aresubstantially perpendicular to the cylindrical contact surface of axialportion 90.

In order to assemble sealing arrangement 172, bearing compartment 56 isassembled by fastening bearing case 64, seal support 66, and heat shield68 together. In addition, most of mid-turbine frame 154 is assembled,such as rod 52 (shown in FIG. 2) and inner case 160, without seal ring162. Then bearing compartment 56 and the partial mid-turbine frame 154are connected. The uninstalled configuration of piston seal 74 has aninner diameter that is smaller than the outer diameter of axial portion90. Therefore, piston seal 74 is expanded into an expanded configurationwith an inner diameter that is larger than the outer diameter of axialportion 90. Piston seal 74 is positioned over heat shield 68 and allowedto contract in order to be in contact with axial portion 90. Piston seal74 grips on to axial portion 90 due to diametic tension, although pistonseal 74 is slidably movable along axial portion 90. Seal ring 162 isthen snapped onto and fastened to inner case 160.

The components and configuration of sealing arrangement 172 as shown inFIG. 4 allow for piston seal 74 to be positioned between mid-turbineframe 154 and bearing compartment 56. Furthermore, assembly anddisassembly of sealing arrangement 172 is relatively simpler and morereliable (as discussed further below). Also, there is much broaderaccess to the contact surfaces on mid-turbine frame 154 and bearingcompartment 56 for inspection and repair purposes.

In FIG. 5, a cross-sectional view of an incorrectly assembled sealingarrangement 172 is shown. More specifically, piston ring 74 has not beenproperly expanded and fit onto heat shield 68 prior to fastening sealring 162 to inner case 160. The components and configuration of sealingarrangement 172 provides an instantly visible indication of incorrectassembly due to gap 196 between seal ring 162 and inner case 160. Gap196 exists because of the relative axial lengths of three of thecomponents of sealing arrangement 172. Length L₁ is the length of snaprim 82 that overlaps snap portion 84. Length L₂ is the length of axialportion 90 that extends beyond piston seal 74, or, in other words,length L₂ is the distance from the end of axial portion 90 to theproximal side of piston seal 74 when piston seal 74 is in the normalsealing position (shown in phantom). Length L₃ is the width of pistonseal 74. Gap 196 exists because length L₁ is shorter than length L₂added to length L₃.

In FIG. 6, a cross-sectional view of sealing arrangement 172 is shown atthe bottom of gas turbine engine 10. At this location of sealingarrangement 172, drain pathway 198A extends axially through seal ring162 proximate axial portion 90. Drain pathway 198B extends radiallythrough seal ring 162 from rabbet 186 into pocket 199. Drain pathway198C extends through the radially outer portion of seal ring 162 at anangle from pocket 199 proximate snap rim 82.

Drain pathways 198A, 198B, and 198C allow for cooling air to purge strayoil that has collected around sealing arrangement 172. Morespecifically, drain pathway 198A allows oil to be blown out into rotorregion 80 by cooling air passing by piston seal 74. In addition, oilthat has accumulated between rabbet 186 and flange 192 is blown outthrough drain pathway 198B, pocket 199, and drain pathway 198C.

In FIG. 7, a cross-sectional view of an alternate embodiment sealingarrangement 272 is shown. In general, sealing arrangement 272 shares theposition of piston seal 74 with sealing arrangements 72 and 172, butfurther includes second seal 275. The addition of second seal 275requires some differently-configured components from that of sealingarrangements 72 and 172.

In the illustrated embodiment, second seal 275 is a w-seal that isformed from a sheet of a high-temperature alloy, such as a nickel orcobalt alloy, which has been folded several times. W-seals are generallycheaper than piston seals and also seal better due to their ability tobe installed in compression. Second seal 275 is positioned betweenmid-turbine frame 254 and bearing compartment 256. More specifically,second seal 275 is configured to contact the radially-extending annularside of second groove 287 in seal ring 262 on one end and an annulararea of radial portion 288 of heat shield 268 on the other end. Thesetwo contact surfaces on second groove 287 and radial portion 288 aresubstantially parallel to each other and are distal from the contactsurfaces for piston seal 74 (i.e. groove 86 and axial portion 290).

The region between seal ring 262 and heat shield 268 that is bordered bypiston seal 74 and second seal 275 is fastener compartment 281.Therefore, there is a leakage flowpath for cooling air that starts incavity 265, goes past piston seal 74, and into fastener compartment 281.This flowpath continues past second seal 275 and into rotor region 80.

In the illustrated embodiment, second seal 275 is positioned directlyradially inwardly of piston seal 74 at the same position alonglongitudinal engine centerline axis C_(L) (shown in FIG. 1) on oppositesides of compartment fastener 278. But second seal 275 is positioned inseries with piston seal 74, downstream along the leakage flowpath frompiston seal 74 during normal flow. In the case of reverse flow, secondseal 275 is positioned upstream of piston seal 74 along the leakageflowpath. In order to better prevent reverse flow, second seal 275 isoriented such that reverse flow tends to force second seal 275 againstsecond groove 287 and radial portion 288 more than in the case of normalflow.

The components and configuration of sealing arrangement 272 as shown inFIG. 7 allow for a cheap and efficient w-seal to be employed (i.e.second seal 275) that is protected by piston seal 74. In addition,sealing arrangement 272 can be better configured to inhibit reverse flowfrom rotor region 80 into cavity 265.

Depicted in FIG. 7 is one embodiment of the present invention, to whichthere are alternative embodiments. For example, second seal 275 can beoriented to better prevent normal flow by reversing its orientation. Foranother example, both piston seal 74 and second seal 275 can be pistonseals. In such an embodiment, second seal 275 would be configured tocontact the annular surface of the radially inner side of second groove287 for inhibiting normal flow and the annular surface of the radiallyouter side of second groove 287 for inhibiting reverse flow.Alternatively, both piston seal 74 and second seal 275 can be w-seals inany combination of orientations. For a further example, piston seal 74can be constrained by the configuration of sealing arrangement 172(shown in FIG. 4).

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

A sealing arrangement according to an exemplary embodiment of thisdisclosure, among other possible things includes: a turbine staticstructure having a first contact surface and a second contact surfacedistal from the first contact surface; a bearing compartment that issurrounded by the turbine static structure having a third contactsurface and a fourth contact surface that is distal from the thirdcontact surface; a cavity between the turbine static structure and thebearing compartment; a first seal positioned between the turbine staticstructure and the bearing compartment, the first seal being configuredto contact the first contact surface and the third contact surface; anda second seal positioned between the turbine static structure and thebearing compartment, the second seal being configured to contact thesecond contact surface and the fourth contact surface.

The sealing arrangement of the preceding paragraph can optionallyinclude, additionally and/or alternatively, any one or more of thefollowing features, configurations and/or additional components:

A further embodiment of the foregoing sealing arrangement, wherein thefirst seal can inhibit forward flow from the cavity into a fastenercompartment, and the second seal inhibits forward flow from the bearingcompartment into a rotor compartment.

A further embodiment of any of the foregoing sealing arrangements,wherein the first seal can be a piston seal.

A further embodiment of any of the foregoing sealing arrangements,wherein the second seal can be a w-seal.

A further embodiment of any of the foregoing sealing arrangements,wherein the w-seal can be configured to be expanded by reverse flow fromthe rotor compartment into the fastener compartment.

A further embodiment of any of the foregoing sealing arrangements,wherein the turbine static structure can further comprise: a fifthcontact surface opposing the first contact surface that the piston sealis configured to contact to inhibit reverse flow from the fastenercompartment into the cavity.

A further embodiment of any of the foregoing sealing arrangements,wherein the turbine static structure further can comprise: an innercase; and a seal ring fastened to the inner case; wherein first andsecond contact surfaces are on the seal ring and the fifth contactsurface is on the inner case.

A further embodiment of any of the foregoing sealing arrangements,wherein the second seal can be directly radially inward of the firstseal.

A further embodiment of any of the foregoing sealing arrangements,wherein the first, second, and fourth contact surfaces can be annularsurfaces.

A further embodiment of any of the foregoing sealing arrangements,wherein the second contact surface can be a cylindrical surface.

A further embodiment of any of the foregoing sealing arrangements,wherein the turbine static structure can further comprise: an innercase; and a seal ring fastened to the inner case; wherein first andsecond contact surfaces are on the seal ring.

A further embodiment of any of the foregoing sealing arrangements,wherein piston seal can be positioned in a groove in the seal ring thatsubstantially surrounds a first side, a second side, and a third side ofthe piston seal.

A further embodiment of any of the foregoing sealing arrangements,wherein the bearing compartment can further comprise: a heat shield;wherein the third and fourth contact surfaces are on the heat shield.

A gas turbine engine, arranged along an axis, according to an exemplaryembodiment of this disclosure, among other possible things includes: afan; a first compressor downstream of the fan; a second compressordownstream of the first compressor; a combustor downstream of the secondcompressor; a first turbine downstream of the combustor; a secondturbine downstream of the first turbine; a turbine static structureproximate at least one of the first turbine and the second turbine; abearing compartment connected to the turbine static structure; a cavitybetween the turbine static structure and the bearing compartment; aflowpath extending from the cavity to one of the first turbine and thesecond turbine, the flowpath being bordered by the turbine staticstructure and the bearing compartment; a first seal positioned betweenthe turbine static structure and the bearing compartment, the first sealbeing configured to contact the turbine static structure and the bearingcompartment during operation of the gas turbine engine that inhibitsflow in the flowpath; and a second seal positioned between the turbinestatic structure and the bearing compartment, the second seal beingconfigured to contact the turbine static structure and the bearingcompartment during operation of the gas turbine engine that inhibitsflow in the flowpath.

The gas turbine engine of the preceding paragraph can optionallyinclude, additionally and/or alternatively, any one or more of thefollowing features, configurations and/or additional components:

A further embodiment of the foregoing gas turbine engine, wherein thefirst seal and the second seal can be positioned at an axial position,with the first seal positioned at a first radial position from the axisand the second seal positioned at a second radial position that isnearer the axis than the first radial position.

A further embodiment of any of the foregoing gas turbine engines,wherein the first seal can be a piston seal and the second seal can be aw-seal.

A further embodiment of any of the foregoing gas turbine engines,wherein the second seal can be configured to expand with flow throughthe flowpath from one of the first and second turbines into the cavity.

A further embodiment of any of the foregoing gas turbine engines,wherein the turbine static structure can be positioned downstream of thefirst turbine and upstream of the second turbine.

A further embodiment of any of the foregoing gas turbine engines,wherein the turbine static structure further can comprise: a gas tube; afairing surrounding the gas tube; an inner case connected to the gastube; and a seal ring fastened to the inner case.

A further embodiment of any of the foregoing gas turbine engines,wherein, during operation of the gas turbine engine: the first seal cancontact a first annular portion of the turbine static structure and acylindrical portion of the bearing compartment during operation of thegas turbine engine; and the second seal can contact a second annularportion of the turbine static structure and a third annular portion ofthe bearing compartment.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. A sealing arrangement comprising: a turbine static structure having afirst contact surface and a second contact surface distal from the firstcontact surface; a bearing compartment that is surrounded by the turbinestatic structure having a third contact surface and a fourth contactsurface that is distal from the third contact surface; a cavity betweenthe turbine static structure and the bearing compartment; a first sealpositioned between the turbine static structure and the bearingcompartment, the first seal being configured to contact the firstcontact surface and the third contact surface; and a second sealpositioned between the turbine static structure and the bearingcompartment, the second seal being configured to contact the secondcontact surface and the fourth contact surface.
 2. The sealingarrangement of claim 1, wherein the first seal inhibits forward flowfrom the cavity into a fastener compartment, and the second sealinhibits forward flow from the bearing compartment into a rotorcompartment.
 3. The sealing arrangement of claim 2, wherein the firstseal is a piston seal.
 4. The sealing arrangement of claim 2, whereinthe second seal is a w-seal.
 5. The sealing arrangement of claim 4,wherein the w-seal is configured to be expanded by reverse flow from therotor compartment into the fastener compartment.
 6. The sealingarrangement of claim 5, wherein the turbine static structure furthercomprises: a fifth contact surface opposing the first contact surfacethat the piston seal is configured to contact to inhibit reverse flowfrom the fastener compartment into the cavity.
 7. The sealingarrangement of claim 6, wherein the turbine static structure furthercomprises: an inner case; and a seal ring fastened to the inner case;wherein first and second contact surfaces are on the seal ring and thefifth contact surface is on the inner case.
 8. The sealing arrangementof claim 1, wherein the second seal is directly radially inward of thefirst seal.
 9. The sealing arrangement of claim 1, wherein the first,second, and fourth contact surfaces are annular surfaces.
 10. Thesealing arrangement of claim 1, wherein the third contact surface is acylindrical surface.
 11. The sealing arrangement of claim 1, wherein theturbine static structure further comprises: an inner case; and a sealring fastened to the inner case; wherein first and second contactsurfaces are on the seal ring.
 12. The sealing arrangement of claim 11,wherein piston seal is positioned in a groove in the seal ring thatsubstantially surrounds a first side, a second side, and a third side ofthe piston seal.
 13. The sealing arrangement of claim 1, wherein thebearing compartment further comprises: a heat shield; wherein the thirdand fourth contact surfaces are on the heat shield.
 14. A gas turbineengine arranged along an axis, the gas turbine engine comprising: a fan;a first compressor downstream of the fan; a second compressor downstreamof the first compressor; a combustor downstream of the secondcompressor; a first turbine downstream of the combustor; a secondturbine downstream of the first turbine; a turbine static structureproximate at least one of the first turbine and the second turbine; abearing compartment connected to the turbine static structure; a cavitybetween the turbine static structure and the bearing compartment; aflowpath extending from the cavity to one of the first turbine and thesecond turbine, the flowpath being bordered by the turbine staticstructure and the bearing compartment; a first seal positioned betweenthe turbine static structure and the bearing compartment, the first sealbeing configured to contact the turbine static structure and the bearingcompartment during operation of the gas turbine engine that inhibitsflow in the flowpath; and a second seal positioned between the turbinestatic structure and the bearing compartment, the second seal beingconfigured to contact the turbine static structure and the bearingcompartment during operation of the gas turbine engine that inhibitsflow in the flowpath.
 15. The gas turbine engine of claim 14, whereinthe first seal and the second seal are positioned at an axial position,with the first seal positioned at a first radial position from the axisand the second seal positioned at a second radial position that isnearer the axis than the first radial position.
 16. The gas turbineengine of claim 14, wherein the first seal is a piston seal and thesecond seal is a w-seal.
 17. The gas turbine engine of claim 16, whereinthe second seal is configured to expand with flow through the flowpathfrom one of the first and second turbines into the cavity.
 18. The gasturbine engine of claim 11, wherein the turbine static structure ispositioned downstream of the first turbine and upstream of the secondturbine.
 19. The gas turbine engine of claim 14, wherein the turbinestatic structure further comprises: a gas tube; a fairing surroundingthe gas tube; an inner case connected to the gas tube; and a seal ringfastened to the inner case.
 20. The gas turbine engine of claim 14,wherein, during operation of the gas turbine engine: the first sealcontacts a first annular portion of the turbine static structure and acylindrical portion of the bearing compartment during operation of thegas turbine engine; and the second seal contacts a second annularportion of the turbine static structure and a third annular portion ofthe bearing compartment.